• K W Patterson, N Noonan, N W Keeling, R Kirkham, and D F Hogan.
• Department of Anaesthesia, St. James's Hospital, Dublin, Ireland.
• J Clin Anesth. 1995 Mar 1; 7 (2): 136-40.

Study ObjectivesTo compare the effects on oxygen saturation as measured by pulse oximetry (SpO2) and ECG changes of endoscopy alone, sedation followed by endoscopy, and sedation followed by endoscopy with supplemental oxygen (O2) during upper gastrointestinal (GI) endoscopy.Study DesignRandomized trial.SettingOutpatient gastroenterology clinic at a university medical center.Patients58 healthy patients scheduled for outpatient upper GI endoscopy, with no clinical evidence of respiratory disease.InterventionsPatients were randomly allocated to three groups: Group 1 received no benzodiazepines before endoscopy and breathed room air throughout (n = 18), Group 2 received midazolam intravenously (i.v.) before endoscopy and breathed room air throughout (n = 20), and Group 3 received i.v. midazolam and 2 L/min O2 through nasal cannulae during endoscopy (Group 3; n = 20).Measurements And Main ResultsData collection, which included heart rate, cardiac rhythm, and SpO2 were recorded at seven intervals: baseline, topical anesthesia of the oropharynx, mouth gag insertion, endoscope insertion, biopsy, endoscope removal, and five minutes postendoscopy. In Group 2, mean SpO2 decreased after midazolam was administered and remained depressed during endoscopy (p < 0.05). After midazolam was given, Group 2 patients differed significantly from patients in Groups 1 and 3 (p < 0.05).ConclusionsThe use of hypnotic doses of benzodiazepines is the primary factor responsible for the reduced oxygenation seen during endoscopy. Neither the presence of the endoscope alone nor the use of midazolam with supplemental O2 caused a decreased oxygenation. This study also suggests that the routine use of benzodiazepines is unnecessary when the endoscopy is of short duration, and the endoscopist employs good topicalization of the oropharynx. In patients who require sedation for endoscopy, O2 administration prevents hypoxemia.

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